a) Field of the Invention
The invention is directed to a pipetting and analyzing device such as is known generically from EP 0 259 386 B1.
b) Description of the Relevant Art
Up to the present time, there is no compact, economical laboratory equipment known from practice which makes it is possible to automatically prepare samples and analyze the prepared samples. Although there are known technical solutions for this purpose such as those described in the references cited in the following, they have presumably not been realized in practice because they are either not flexible enough or are not economical.
EP 0 259 386 B1 describes a photometric analyzing device which, in contrast to the state of the art in 1986, allowed a completely monitored analyzing process from preparation of samples to evaluation of the results of photometric measurements. This analyzing device disclosed in EP 0 259 386 B1 comprises:                a primary rack for holding a large number of sample tubes        a mechanical table which holds a microtitration plate and is arranged alongside the primary rack and which can be positioned in any desired X-Y direction in a lower horizontal plane        a sample distributor arm which is arranged above the primary rack and mechanical table and which can be positioned in any desired manner in an upper horizontal plane        a photometer which is arranged within the positioning area of the mechanical table and whose beam path vertically pierces the X-Y plane of the mechanical table, and a programmable computer for controlling the entire photometric analyzing device.        
The sample distributor arm advantageously has a vertically movable single-channel pipette and the device can additionally comprise an incubator or a rinse liquid trough.
U.S. Pat. No. 5,443,790 discloses an analysis device for samples which, like the device described in EP 0 259 386 B1, allows the preparation of the samples to be analyzed in reaction vessels (reaction carriers in EP 0 259 386; wells of a microtitration plate in U.S. Pat. No. 5,443,790), a thermal regulation of the samples located in the reaction vessels and the analysis of the samples through photometric measurement.
In order to prepare the samples, the required liquids which are provided in vessels supplied for this purpose on the work platform are added to and removed from the reaction vessels in predetermined amounts and in a given sequence. For this purpose, the reaction vessels are located in a defined position on the work platform of the respective device. A pipetting head (sample distributor arm in EP 0 259 386, head in U.S. Pat. No. 5,443,790) located above the work platform is driven in a horizontal plane in X-Y direction above the work platform.
In order to regulate the temperature of the samples and for analysis, the reaction vessels which are positioned on an X-Y mechanical table in EP 0 259 386 and which are embodied in practice by the wells of a microtitration plate are moved into an incubator or into the beam path of a photometer. It is apparent that this mechanical table has its own drive unit and its own control.
In contrast, the reaction vessels in the apparatus described in U.S. Pat. No. 5,443,790 remain in their defined rigid position also for the purpose of regulating temperature and analysis on the work platform.
The reaction vessels can remain in this position for regulating temperature because they are held immersed in a reservoir (bath) filled with a liquid whose temperature can be regulated. Insofar as the reaction vessels must be adjusted to different temperatures during the preparation process, this type of stationary arrangement of the reaction vessels is disadvantageous because the temperature of the reaction vessels and of the contained samples can only change slowly due to the high heat capacity of the liquid in the bath and because they must remain in the bath. It is always possible to adjust the temperature more rapidly by inserting into and removing from a preheated incubator.
The reaction vessels can also remain in their defined rigid position for analyzing the samples because provision is made for removing the sample to be analyzed from the respective reaction vessel and moving it to a vessel arranged in the beam path of the photometer, namely in this case over an opening in the working plane. Accordingly, aside from the vertical translatory movement (Z-direction) that is always necessary, the entire movement process of the device described in U.S. Pat. No. 5,443,790 is realized solely through the horizontal translatory movement of the pipetting head in the X-Y direction. Therefore, the design of the device is simpler because only the pipetting head need be driven and controlled. It must be assumed that the vessels for the samples to be analyzed are exchanged manually.
This solution has the decisive disadvantage that the sample to be analyzed must be transferred by pipetting. The limited applicability of the device to samples (reagent products) that are actually liquid is also disadvantageous.